Effects of heat shock on glucocorticoid receptor.

The changes of glucocorticoid receptor (GR) during the heat shock response have been studied using a human osteosarcoma cell line (HOS-8603) as the model. The expression of the heat shock protein 70 (hsp70) mRNA in HOS-8603 cells has been enhanced markedly after a heat treatment at 43 degrees C for 30 min. A mild thermal pretreatment (42 degrees C for 1 h) protects the HOS-8603 cells against a subsequent heat challenge (46 degrees C). This induced thermotolerance is reflected by the increase of cell viability of HOS-8603 cells. The GR binding activity in HOS-8603 cells decreased rapidly after the heat treatment at 43 degrees C; only 42.61% of controls were detected 60 min after the heat treatment. However, there was no significant change in the dissociation constant value (Kd). These results indicate that the heat shock induce not only the heat shock mRNA expression, but also the rapid reduction in GR binding activity, suggesting that there might be a functional relationship between GR action and the heat shock response.